Re: [PATCH 5/7] mm: rework reclaim_stat counters

[Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>]

KAMEZAWA Hiroyuki wrote:
> On Wed, 29 Feb 2012 13:15:56 +0400
> Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>  wrote:
>
> > Currently there is two types of reclaim-stat counters:
> > recent_scanned (pages picked from from lru),
> > recent_rotated (pages putted back to active lru).
> > Reclaimer uses ratio recent_rotated / recent_scanned
> > for balancing pressure between file and anon pages.
> >
> > But if we pick page from lru we can either reclaim it or put it back to lru, thus:
> > recent_scanned == recent_rotated[inactive] + recent_rotated[active] + reclaimed
> > This can be called "The Law of Conservation of Memory" =)
> I'm sorry....where is the count for active->incative ?

If reclaimer deactivates page it will bump recent_rotated[LRU_INACTIVE_ANON/FILE],
(if I understand your question right) recent_rotated[] now count each evictable lru independently

> > Thus recent_rotated counters for each lru list is enough, reclaimed pages can be
> > counted as rotatation into inactive lru. After that reclaimer can use this ratio:
> > recent_rotated[active] / (recent_rotated[active] + recent_rotated[inactive])
> >
> > After this patch struct zone_reclaimer_stat has only one array: recent_rotated,
> > which is directly indexed by lru list index.
> >
> > Signed-off-by: Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>
>
> I'm sorry if I misunderstand..
> Recent_scanned can be update by some logics other than vmscan..
>
> For example, how lru_deactivate_fn() is handled ?

It increase recent_rotated[LRU_INACTIVE_ANON/LRU_INACTIVE_FILE]

> Thanks,
> -Kame
>
>
>
>
> > ---
> >   include/linux/mmzone.h |   11 +++++------
> >   mm/memcontrol.c        |   29 +++++++++++++++++------------
> >   mm/page_alloc.c        |    6 ++----
> >   mm/swap.c              |   26 ++++++++------------------
> >   mm/vmscan.c            |   42 ++++++++++++++++++++++--------------------
> >   5 files changed, 54 insertions(+), 60 deletions(-)
> >
> > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> > index 2fed935..fdcd683 100644
> > --- a/include/linux/mmzone.h
> > +++ b/include/linux/mmzone.h
> > @@ -137,12 +137,14 @@ enum lru_list {
> >        LRU_INACTIVE_FILE = LRU_BASE + LRU_FILE,
> >        LRU_ACTIVE_FILE = LRU_BASE + LRU_FILE + LRU_ACTIVE,
> >        LRU_UNEVICTABLE,
> > -     NR_LRU_LISTS
> > +     NR_LRU_LISTS,
> > +     NR_EVICTABLE_LRU_LISTS = LRU_UNEVICTABLE,
> >   };
> >
> >   #define for_each_lru(lru) for (lru = 0; lru<  NR_LRU_LISTS; lru++)
> >
> > -#define for_each_evictable_lru(lru) for (lru = 0; lru<= LRU_ACTIVE_FILE; lru++)
> > +#define for_each_evictable_lru(lru) \
> > +     for (lru = 0; lru<  NR_EVICTABLE_LRU_LISTS; lru++)
> >
> >   static inline int is_file_lru(enum lru_list lru)
> >   {
> > @@ -165,11 +167,8 @@ struct zone_reclaim_stat {
> >         * mem/swap backed and file backed pages are refeferenced.
> >         * The higher the rotated/scanned ratio, the more valuable
> >         * that cache is.
> > -      *
> > -      * The anon LRU stats live in [0], file LRU stats in [1]
> >         */
> > -     unsigned long           recent_rotated[2];
> > -     unsigned long           recent_scanned[2];
> > +     unsigned long           recent_rotated[NR_EVICTABLE_LRU_LISTS];
> >   };
> >
> >   struct lruvec {
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index aeebb9e..2809531 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -4189,26 +4189,31 @@ static int mem_control_stat_show(struct cgroup *cont, struct cftype *cft,
> >
> >   #ifdef CONFIG_DEBUG_VM
> >        {
> > -             int nid, zid;
> > +             int nid, zid, lru;
> >                struct mem_cgroup_per_zone *mz;
> >                struct zone_reclaim_stat *rstat;
> > -             unsigned long recent_rotated[2] = {0, 0};
> > -             unsigned long recent_scanned[2] = {0, 0};
> > +             unsigned long recent_rotated[NR_EVICTABLE_LRU_LISTS];
> >
> > +             memset(recent_rotated, 0, sizeof(recent_rotated));
> >                for_each_online_node(nid)
> >                        for (zid = 0; zid<  MAX_NR_ZONES; zid++) {
> >                                mz = mem_cgroup_zoneinfo(memcg, nid, zid);
> >                                rstat =&mz->lruvec.reclaim_stat;
> > -
> > -                             recent_rotated[0] += rstat->recent_rotated[0];
> > -                             recent_rotated[1] += rstat->recent_rotated[1];
> > -                             recent_scanned[0] += rstat->recent_scanned[0];
> > -                             recent_scanned[1] += rstat->recent_scanned[1];
> > +                             for_each_evictable_lru(lru)
> > +                                     recent_rotated[lru] +=
> > +                                             rstat->recent_rotated[lru];
> >                        }
> > -             cb->fill(cb, "recent_rotated_anon", recent_rotated[0]);
> > -             cb->fill(cb, "recent_rotated_file", recent_rotated[1]);
> > -             cb->fill(cb, "recent_scanned_anon", recent_scanned[0]);
> > -             cb->fill(cb, "recent_scanned_file", recent_scanned[1]);
> > +
> > +             cb->fill(cb, "recent_rotated_anon",
> > +                             recent_rotated[LRU_ACTIVE_ANON]);
> > +             cb->fill(cb, "recent_rotated_file",
> > +                             recent_rotated[LRU_ACTIVE_FILE]);
> > +             cb->fill(cb, "recent_scanned_anon",
> > +                             recent_rotated[LRU_ACTIVE_ANON] +
> > +                             recent_rotated[LRU_INACTIVE_ANON]);
> > +             cb->fill(cb, "recent_scanned_file",
> > +                             recent_rotated[LRU_ACTIVE_FILE] +
> > +                             recent_rotated[LRU_INACTIVE_FILE]);
> >        }
> >   #endif
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index ab2d210..ea40034 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -4365,10 +4365,8 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
> >                zone_pcp_init(zone);
> >                for_each_lru(lru)
> >                        INIT_LIST_HEAD(&zone->lruvec.lists[lru]);
> > -             zone->lruvec.reclaim_stat.recent_rotated[0] = 0;
> > -             zone->lruvec.reclaim_stat.recent_rotated[1] = 0;
> > -             zone->lruvec.reclaim_stat.recent_scanned[0] = 0;
> > -             zone->lruvec.reclaim_stat.recent_scanned[1] = 0;
> > +             memset(&zone->lruvec.reclaim_stat, 0,
> > +                             sizeof(struct zone_reclaim_stat));
> >                zap_zone_vm_stats(zone);
> >                zone->flags = 0;
> >                if (!size)
> > diff --git a/mm/swap.c b/mm/swap.c
> > index 9a6850b..c7bcde7 100644
> > --- a/mm/swap.c
> > +++ b/mm/swap.c
> > @@ -277,7 +277,7 @@ void rotate_reclaimable_page(struct page *page)
> >   }
> >
> >   static void update_page_reclaim_stat(struct zone *zone, struct page *page,
> > -                                  int file, int rotated)
> > +                                  enum lru_list lru)
> >   {
> >        struct zone_reclaim_stat *reclaim_stat;
> >
> > @@ -285,9 +285,7 @@ static void update_page_reclaim_stat(struct zone *zone, struct page *page,
> >        if (!reclaim_stat)
> >                reclaim_stat =&zone->lruvec.reclaim_stat;
> >
> > -     reclaim_stat->recent_scanned[file]++;
> > -     if (rotated)
> > -             reclaim_stat->recent_rotated[file]++;
> > +     reclaim_stat->recent_rotated[lru]++;
> >   }
> >
> >   static void __activate_page(struct page *page, void *arg)
> > @@ -295,7 +293,6 @@ static void __activate_page(struct page *page, void *arg)
> >        struct zone *zone = page_zone(page);
> >
> >        if (PageLRU(page)&&  !PageActive(page)&&  !PageUnevictable(page)) {
> > -             int file = page_is_file_cache(page);
> >                int lru = page_lru_base_type(page);
> >                del_page_from_lru_list(zone, page, lru);
> >
> > @@ -304,7 +301,7 @@ static void __activate_page(struct page *page, void *arg)
> >                add_page_to_lru_list(zone, page, lru);
> >                __count_vm_event(PGACTIVATE);
> >
> > -             update_page_reclaim_stat(zone, page, file, 1);
> > +             update_page_reclaim_stat(zone, page, lru);
> >        }
> >   }
> >
> > @@ -482,7 +479,7 @@ static void lru_deactivate_fn(struct page *page, void *arg)
> >
> >        if (active)
> >                __count_vm_event(PGDEACTIVATE);
> > -     update_page_reclaim_stat(zone, page, file, 0);
> > +     update_page_reclaim_stat(zone, page, lru);
> >   }
> >
> >   /*
> > @@ -646,9 +643,7 @@ EXPORT_SYMBOL(__pagevec_release);
> >   void lru_add_page_tail(struct zone* zone,
> >                       struct page *page, struct page *page_tail)
> >   {
> > -     int active;
> >        enum lru_list lru;
> > -     const int file = 0;
> >
> >        VM_BUG_ON(!PageHead(page));
> >        VM_BUG_ON(PageCompound(page_tail));
> > @@ -660,13 +655,10 @@ void lru_add_page_tail(struct zone* zone,
> >        if (page_evictable(page_tail, NULL)) {
> >                if (PageActive(page)) {
> >                        SetPageActive(page_tail);
> > -                     active = 1;
> >                        lru = LRU_ACTIVE_ANON;
> > -             } else {
> > -                     active = 0;
> > +             } else
> >                        lru = LRU_INACTIVE_ANON;
> > -             }
> > -             update_page_reclaim_stat(zone, page_tail, file, active);
> > +             update_page_reclaim_stat(zone, page_tail, lru);
> >        } else {
> >                SetPageUnevictable(page_tail);
> >                lru = LRU_UNEVICTABLE;
> > @@ -694,17 +686,15 @@ static void __pagevec_lru_add_fn(struct page *page, void *arg)
> >   {
> >        enum lru_list lru = (enum lru_list)arg;
> >        struct zone *zone = page_zone(page);
> > -     int file = is_file_lru(lru);
> > -     int active = is_active_lru(lru);
> >
> >        VM_BUG_ON(PageActive(page));
> >        VM_BUG_ON(PageUnevictable(page));
> >        VM_BUG_ON(PageLRU(page));
> >
> >        SetPageLRU(page);
> > -     if (active)
> > +     if (is_active_lru(lru))
> >                SetPageActive(page);
> > -     update_page_reclaim_stat(zone, page, file, active);
> > +     update_page_reclaim_stat(zone, page, lru);
> >        add_page_to_lru_list(zone, page, lru);
> >   }
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 483b98e..fe00a22 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -1355,11 +1355,7 @@ putback_inactive_pages(struct mem_cgroup_zone *mz,
> >                SetPageLRU(page);
> >                lru = page_lru(page);
> >                add_page_to_lru_list(zone, page, lru);
> > -             if (is_active_lru(lru)) {
> > -                     int file = is_file_lru(lru);
> > -                     int numpages = hpage_nr_pages(page);
> > -                     reclaim_stat->recent_rotated[file] += numpages;
> > -             }
> > +             reclaim_stat->recent_rotated[lru] += hpage_nr_pages(page);
> >                if (put_page_testzero(page)) {
> >                        __ClearPageLRU(page);
> >                        __ClearPageActive(page);
> > @@ -1543,8 +1539,11 @@ shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz,
> >
> >        spin_lock_irq(&zone->lru_lock);
> >
> > -     reclaim_stat->recent_scanned[0] += nr_anon;
> > -     reclaim_stat->recent_scanned[1] += nr_file;
> > +     /*
> > +      * Count reclaimed pages as rotated, this helps balance scan pressure
> > +      * between file and anonymous pages in get_scan_ratio.
> > +      */
> > +     reclaim_stat->recent_rotated[lru] += nr_reclaimed;
> >
> >        if (current_is_kswapd())
> >                __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
> > @@ -1685,8 +1684,6 @@ static void shrink_active_list(unsigned long nr_to_scan,
> >        if (global_reclaim(sc))
> >                zone->pages_scanned += nr_scanned;
> >
> > -     reclaim_stat->recent_scanned[file] += nr_taken;
> > -
> >        __count_zone_vm_events(PGREFILL, zone, nr_scanned);
> >        __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken);
> >        __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
> > @@ -1742,7 +1739,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
> >         * helps balance scan pressure between file and anonymous pages in
> >         * get_scan_ratio.
> >         */
> > -     reclaim_stat->recent_rotated[file] += nr_rotated;
> > +     reclaim_stat->recent_rotated[lru] += nr_rotated;
> >
> >        move_active_pages_to_lru(zone,&l_active,&l_hold, lru);
> >        move_active_pages_to_lru(zone,&l_inactive,&l_hold, lru - LRU_ACTIVE);
> > @@ -1875,6 +1872,7 @@ static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
> >        unsigned long anon_prio, file_prio;
> >        unsigned long ap, fp;
> >        struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
> > +     unsigned long *recent_rotated = reclaim_stat->recent_rotated;
> >        u64 fraction[2], denominator;
> >        enum lru_list lru;
> >        int noswap = 0;
> > @@ -1940,14 +1938,16 @@ static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
> >         * anon in [0], file in [1]
> >         */
> >        spin_lock_irq(&mz->zone->lru_lock);
> > -     if (unlikely(reclaim_stat->recent_scanned[0]>  anon / 4)) {
> > -             reclaim_stat->recent_scanned[0] /= 2;
> > -             reclaim_stat->recent_rotated[0] /= 2;
> > +     if (unlikely(recent_rotated[LRU_INACTIVE_ANON] +
> > +                  recent_rotated[LRU_ACTIVE_ANON]>  anon / 4)) {
> > +             recent_rotated[LRU_INACTIVE_ANON] /= 2;
> > +             recent_rotated[LRU_ACTIVE_ANON] /= 2;
> >        }
> >
> > -     if (unlikely(reclaim_stat->recent_scanned[1]>  file / 4)) {
> > -             reclaim_stat->recent_scanned[1] /= 2;
> > -             reclaim_stat->recent_rotated[1] /= 2;
> > +     if (unlikely(recent_rotated[LRU_INACTIVE_FILE] +
> > +                  recent_rotated[LRU_ACTIVE_FILE]>  file / 4)) {
> > +             recent_rotated[LRU_INACTIVE_FILE] /= 2;
> > +             recent_rotated[LRU_ACTIVE_FILE] /= 2;
> >        }
> >
> >        /*
> > @@ -1955,11 +1955,13 @@ static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
> >         * proportional to the fraction of recently scanned pages on
> >         * each list that were recently referenced and in active use.
> >         */
> > -     ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
> > -     ap /= reclaim_stat->recent_rotated[0] + 1;
> > +     ap = (anon_prio + 1) * (recent_rotated[LRU_INACTIVE_ANON] +
> > +                             recent_rotated[LRU_ACTIVE_ANON] + 1);
> > +     ap /= recent_rotated[LRU_ACTIVE_ANON] + 1;
> >
> > -     fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
> > -     fp /= reclaim_stat->recent_rotated[1] + 1;
> > +     fp = (file_prio + 1) * (recent_rotated[LRU_INACTIVE_FILE] +
> > +                             recent_rotated[LRU_ACTIVE_FILE] + 1);
> > +     fp /= recent_rotated[LRU_ACTIVE_FILE] + 1;
> >        spin_unlock_irq(&mz->zone->lru_lock);
> >
> >        fraction[0] = ap;
>
> --
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